1. Field of the Invention
This invention relates to an automatic fire-extinguishing device for an oil burner, and more particularly to an automatic fire-extinguishing device for a wick-ignition type oil burner adapted to vertically move a wick for ignition and fire-extinguishing.
2. Description of the Prior Art
In a wick-ignition type oil burner, fire-extinguishing is generally carried out by lowering a wick in a wick receiving construction. For the purpose of automatic fire-extinguishing of an oil burner, an automatic fire-extinguishing device was proposed which is constructed to rotate a gear which has a return spring loosely fitted on a wick operating shaft to wind up the return spring and then engage the gear with a stopper to hold the return spring at a wound-up state during the operation of raising the wick to a wick raising position or ignition position. In an emergency such as earthquake or the like, the wound-up return spring is released from the stopper to forcibly lower the wick to a wick lowering position or fire-extinguishing position to attain fire-extinguishing.
Also, in relation to such a fire-extinguishing device, a device for adjusting a vertical position of a wick was proposed as disclosed in Japanese Utility Model Application No. 77541/1979 filed by the assignee, which is so constructed that a holding plate rotated with a gear selects a desired one of teeth of the gear which is to be engaged with a stopper at a wick raising position, to thereby adjust a vertical position of the wick.
In the conventional fire-extinguishing device, the gear which is engaged with the stopper to hold the return spring at a wound-up state is constantly applied thereto force of the return spring, accordingly, great operating force is required to release the stopper from engagement with the gear in an emergency. Also, this causes a variation in the operating force to be increased. In order to accommodate such problems, it was proposed to make the gear of a material having a low friction coefficient such as plastic or the like or subject it to a surface treatment to decrease friction between the gear and the stopper. Unfortunately, such a plastic material is inferior in impact strength, and materials of a low friction other than plastic are generally expensive. Also, the surface treatment is costly.
In the conventional automatic fire-extinguishing device, disengagement of the stopper from the gear in an emergency is carried out by tilting or bringing down a vibration sensing weight to actuate the stopper. The vibration sensing weight is divided into two types or a self-standing type and an outside-help type. In the former type, the weight is constructed to have a small tilting angle, accordingly, it is required to manufacture parts constituting the weight with high accuracy; whereas the latter type is adapted to be manually reset through a suitable means such as a set lever or the like, resulting in being highly troublesome.
In view of such disadvantages, a weight reset device was proposed which is disclosed in Japanese Utility Model No. 156960/1978 filed by the assignee. In the device, a spring is arranged to force a stopper against a gear and the gear is formed with a tooth-less portion at a position thereof which is rendered opposite to the stopper when a wick is lowered to a fire-extinguishing position, so that the spring forces the stopper against the tooth-less portion of the gear to reset or raise up the weight through a stopper actuating plate of the weight operatively connected to the stopper. However, this is still insufficient to positively and effectively automatically reset the weight.
Also, Japanese utility Model Application Nos. 114182/1978 and 180951/1979 each disclose a structure that a wick operating shaft actuates a set lever for resetting or raising up a tilted vibration sensing weight at a fire-extinguishing position. Unfortunately, such a structure causes a fire-extinguishing device to be highly complicated in construction, resulting in an oil burner being large-sized and expensive.
Accordingly, it would be highly desirable to develop an automatic fire-extinguishing device for an oil burner which is capable of being actuated with high accuracy, being manufactured with a low cost, positively setting up a vibration sensing weight in a simple manner.